1. Field of the Invention
The present invention relates to a blood pressure monitor including an inflatable cuff.
2. Related Art Statement
There is known a blood pressure (BP) monitor which includes an inflatable cuff adapted to be wound around a body portion, e.g., upper arm, of a living subject, e.g., patient, to press the body portion. The BP monitor functions as an automatic BP measuring device which periodically measures a BP value of the subject by increasing the cuff pressure and thereby pressing the body portion of the subject. However, if the period or interval of the BP measurements effected by the BP monitor is shortened for improving the accuracy of monitoring of subject""s blood pressure, the frequency of pressing of subject""s body portion is increased, which causes the subject to feel discomfort.
In the above-indicated background, it has been proposed to increase the pressure of an inflatable cuff being wound around a body portion of a living subject, up to a predetermined value, detect a pulse wave that is a pressure oscillation produced in the cuff, and estimate a BP value of the subject based on the magnitude of the pulse wave. This technique is disclosed in, e.g., Japanese Patent Application laid open for inspection purposes under Publication No. 61(1986)-103432, or Japanese Patent Application laid open for inspection purposes under Publication No. 60(1985)-241422.
Regarding the above-indicated conventional BP monitor techniques, however, there are known some cases where it is difficult to detect a change of magnitudes of pulse waves which reflects a change of blood pressure of a living subject, if BP values are estimated based on the pulse waves detected at a considerably low cuff pressure, which contributes to reducing the discomfort felt by the subject. More specifically described, respective amplitudes of pulses of a pulse wave which is detected from an inflatable cuff being wound around a body portion of a living subject whose blood pressure is normal, has an envelope indicated at solid line in the graph of FIG. 6. In contrast, amplitudes of pulses of a pulse wave obtained from a living subject whose blood pressure is low, has an envelope indicated at one-dot chain line in FIG. 6. In the case where amplitudes of pulses of a pulse wave are detected at a considerably low cuff pressure, e.g., pressure, PK, in FIG. 6, an amount of change of the pulse amplitudes with respect to an amount of change of blood pressure of a living subject may be too small. Thus, when the BP monitor is used at the low cuff pressure PK, it may not be able to monitor the blood pressure of the subject with high accuracy.
There is also known a continuous BP monitor which includes an inflatable cuff which is adapted to be wound around a body portion of a living subject to press the body portion; a blood pressure measuring device which measures a blood pressure of the subject by changing a pressure in the cuff; a pressure pulse wave sensor which is adapted to be pressed against a distal section of the artery located on a distal side of the cuff wound around the body portion, so as to detect a pressure pulse wave which is produced from the distal section of the artery; a relationship determining means which determines a relationship between blood pressure and magnitude of pressure pulse wave, based on the blood pressure measured by the blood pressure measuring device and a magnitude of the pressure pulse wave detected by the pressure pulse wave sensor; a blood pressure determining means which successively determines a blood pressure of the subject according to the determined relationship based on a magnitude of each of successive heartbeat-synchronous pulses of the pressure pulse wave detected by the pressure pulse wave sensor; and a display which displays the blood pressure values determined by the blood pressure determining means. This BP monitor is disclosed in, e.g., Japanese Patent Application laid open for inspection purposes under Publication No. 1(1989)-214338 or Japanese Utility Model Application laid open for inspection purposes under Publication No. 2(1990)-82309.
In the prior continuous BP monitor, the condition under which the pressure pulse wave sensor is pressed against subject""s artery may be changed due to, e.g., a physical motion of the subject. Hence, in order to improve the accuracy of BP values determined by the BP determining means, the relationship between blood pressure and magnitude of pressure pulse wave is updated at a predetermined period. However, the updating of the relationship needs a blood pressure measurement of the blood pressure measuring device including the inflation of the cuff. In addition, since the pressure pulse wave sensor is set on the distal side of the cuff, the continuous BP determination of the BP determining means is interrupted by the inflation of the cuff. This problem is exaggerated if the period of updating of the relationship is shortened for improving the accuracy of the continuous BP monitoring.
It is a first object of the present invention to provide a blood pressure monitor which includes an inflatable cuff and which monitors with high accuracy the blood pressure of a living subject without causing the subject to feel discomfort.
It is a second object of the present invention to provide a continuous blood pressure monitor which includes an inflatable cuff and which continuously monitors the blood pressure of a living subject with reduced discomfort felt by the subject and with reduced interruption frequency.
The first object may be achieved according to a first aspect of the present invention, which provides a blood pressure monitor including an inflatable cuff which is adapted to be wound around a body portion of a living subject to press the body portion, a pressure sensor which detects a pressure in the cuff, a cuff-pressure regulating device which increases the pressure of the cuff, pulse-amplitude determining means for determining an amplitude of each of pulses of a pulse wave which are produced in the cuff and detected by the pressure sensor while the pressure of the cuff is increased by the cuff-pressure regulating device, candidate determining means for determining, as a diastolic blood pressure candidate, a pressure of the cuff which is detected by the pressure sensor and which corresponds to an amplitude of a first pulse of the pulses determined by the pulse-amplitude determining means, by judging whether the amplitude of the first pulse is not greater than a reference value which is smaller than an amplitude of at least one second pulse of the pulses, by a predetermined proportion of the amplitude of the second pulse, the amplitude of the second pulse being determined by the pulse-amplitude determining means after the amplitude of the first pulse is determined, and blood-pressure determining means for determining, as a monitor diastolic blood pressure value, the pressure of the cuff corresponding to the amplitude of the first pulse, when the candidate determining means determines, as the diastolic blood pressure candidate, the pressure of the cuff corresponding to the amplitude of the first pulse, with respect to a predetermined number of the at least one second pulse.
In the blood pressure (BP) monitor in accordance with the first aspect of the invention, the predetermined number may be one, two, or a greater number. For example, the predetermined number is three. Thus, the present BP monitor may determine a monitor diastolic BP value of a living subject at a pressure level which is higher than the diastolic BP value and which corresponds to the xe2x80x9cthirdxe2x80x9d one of the subsequent pulses determined after the initial pulse. The thus determined monitor diastolic BP value enjoys high accuracy. In addition, since the pressure level where the monitor diastolic BP value is determined is considerably low, the subject does not feel discomfort.
According to a preferred feature of the first aspect of the invention, the candidate determining means comprises judging means for judging whether the amplitude of the first pulse is not greater than a reference value which is smaller than an amplitude of each of a plurality of second pulses of the pulses, by a predetermined proportion of the amplitude of the each second pulse, the respective amplitudes of the second pulses being determined by the pulse-amplitude determining means after the amplitude of the first pulse is determined.
According to another feature of the first aspect of the invention, the cuff-pressure regulating device comprises pressure increasing means for stepwise increasing the pressure of the cuff by alternately increasing the cuff pressure and maintaining the cuff pressure at each of a plurality of different pressure values, and the pulse-amplitude determining means determines an amplitude of at least one pulse which is produced in the cuff and detected by the pressure sensor while the cuff pressure is maintained at the each pressure value. The pressure increasing means may increase the cuff pressure by a constant pressure increase amount, for each time or step, or may increase the cuff pressure by an increase amount which is variable depending upon the current cuff pressure. The pulse-amplitude determining means may determine an amplitude of a single pulse detected by the pressure sensor while the cuff pressure is maintained at each pressure value, or an average of respective amplitudes of two or more pulses detected while the cuff pressure is maintained at each pressure value. The thus determined pulse amplitude or amplitudes enjoy high accuracy because they are free from adverse influences resulting from the increasing of the cuff pressure. Therefore, the monitor diastolic BP values of the subject are determined with accuracy based on the pulse amplitudes.
According to another feature of the first aspect of the invention, the blood-pressure determining means comprises monitor means for iteratively determining the monitor diastolic blood pressure value. The monitor means may periodically determine the monitor diastolic blood pressure value at a predetermined period or interval of time (i.e., monitor cycle time).
According to another feature of the first aspect of the invention, the BP monitor further comprises abnormality identifying means for identifying an abnormality of the monitor diastolic blood pressure values iteratively determined by the monitor means.
According to another feature of the first aspect of the invention, the abnormality identifying means comprises means for identifying the abnormality based on at least one of an amount of change of a last determined value of the monitor diastolic blood pressure values from an average of the monitor diastolic blood pressure values, and a rate of change of the last determined value of the monitor diastolic blood pressure values from the average of the monitor diastolic blood pressure values.
According to another feature of the first aspect of the invention, the BP monitor further comprising a blood pressure measuring device which increases the pressure of the cuff up to a target pressure which is higher than a systolic blood pressure of the subject and measures at least one of a systolic, a mean, and a diastolic blood pressure value of the living subject based on a variation of respective amplitudes of pulses of a pulse wave which are produced in the cuff and detected by the pressure sensor during at least one of the increasing of the cuff pressure up to the target pressure and a decreasing of the cuff pressure down from the target pressure. The target pressure may be, e.g., about 180 mmHg that is estimated to be sufficiently higher than a normal systolic BP value of a human being.
According to another feature of the first aspect of the invention, the blood pressure measuring device comprises means for measuring the at least one of the systolic, the mean, and the diastolic blood pressure value of the living subject when the abnormality identifying means identifies the abnormality.
According to another feature of the first aspect of the invention, the BP monitor further comprising a display which displays the monitor diastolic blood pressure value determined by the blood-pressure determining means.
The second object may be achieved according to a second aspect of the present invention, which provides a blood pressure monitor comprising an inflatable cuff which is adapted to be wound around a body portion of a living subject to press the body portion through which an artery of the subject extends; a blood pressure measuring device which measures a blood pressure of the subject by changing a pressure in the cuff; a pressure pulse wave sensor which is adapted to be pressed against a distal section of the artery located on a distal side of the cuff wound around the body portion, so as to detect a pressure pulse wave which is produced from the distal section of the artery and is propagated thereto via a skin tissue above the distal section; relationship determining means for determining a relationship between blood pressure and magnitude of pressure pulse wave, based on the blood pressure measured by the blood pressure measuring device and a magnitude of the pressure pulse wave detected by the pressure pulse wave sensor; blood pressure determining means for successively determining at least a diastolic blood pressure of the subject according to the determined relationship based on a magnitude of a lower-peak point of each of successive first heartbeat-synchronous pulses of the pressure pulse wave detected by the pressure pulse wave sensor; cuff-pressure increasing means for increasing the pressure of the cuff at a predetermined rate; waveform-characteristic determining means for determining a characteristic of a lower-peak portion of a waveform of each of successive second heartbeat-synchronous pulses of the pressure pulse wave which are detected by the pressure pulse wave sensor when the pressure of the cuff is increased at the predetermined rate by the cuff-pressure increasing means, the lower-peak portion including a lower-peak point of the each second heartbeat-synchronous pulse; and judging means for judging whether the determined relationship is accurate, based on at least one diastolic blood pressure determined by the blood pressure determining means and a pressure of the cuff corresponding to a time when the waveform characteristics determined by the waveform characteristic determining means significantly largely change.
In the blood pressure monitor in accordance with the second aspect of the invention, if the judging means makes a positive judgment, the relationship need not be updated. Accordingly, the blood pressure measuring device does not inflate the cuff, and the subject is prevented from being pressed by the cuff. In addition, although the pressure pulse wave sensor is set on the distal side of the cuff, the blood pressure determining means can continue to successively determine blood pressure values according to the relationship based on the pressure pulse wave detected by the pressure pulse wave sensor.
The second object may be achieved according to a third aspect of the present invention, which provides a blood pressure monitor comprising an inflatable cuff which is adapted to be wound around a body portion of a living subject to press the body portion through which an artery of the subject extends; a blood pressure measuring device which measures a blood pressure of the subject by changing a pressure in the cuff; a pressure pulse wave sensor which is adapted to be pressed against a distal section of the artery located on a distal side of the cuff wound around the body portion, so as to detect a pressure pulse wave which is produced from the distal section of the artery and is propagated thereto via a skin tissue above the distal section; relationship determining means for determining a relationship between blood pressure and magnitude of pressure pulse wave, based on the blood pressure measured by the blood pressure measuring device and a magnitude of the pressure pulse wave detected by the pressure pulse wave sensor; blood pressure determining means for determining at least a diastolic blood pressure of the subject according to the determined relationship based on a magnitude of a lower-peak point of each of successive first heartbeat-synchronous pulses of the pressure pulse wave detected by the pressure pulse wave sensor; cuff-pressure increasing means for increasing the pressure of the cuff at a predetermined rate; a cuff pulse wave sensor which detects a cuff pulse wave which is a pressure oscillation produced in the cuff; phase-difference determining means for determining a phase difference of respective lower-peak points of each of successive second heartbeat-synchronous pulses of the pressure pulse wave and a corresponding one of successive heartbeat-synchronous pulses of the cuff pulse wave, the second heartbeat-synchronous pulses of the pressure pulse wave and the heartbeat-synchronous pulses of the cuff pulse wave being detected by the pressure pulse wave sensor and the cuff pulse wave sensor, respectively, when the pressure of the cuff is increased at the predetermined rate by the cuff-pressure increasing means; and judging means for judging whether the determined relationship is accurate, based on at least one diastolic blood pressure determined by the blood pressure determining means and a pressure of the cuff corresponding to a time when the phase differences determined by the phase-difference determining means significantly largely change.
In the blood pressure monitor in accordance with the third aspect of the invention, if the judging means makes a positive judgment, the relationship need not be updated. Accordingly, the blood pressure measuring device does not inflate the cuff, and the subject is prevented from being pressed by the cuff. In addition, although the pressure pulse wave sensor is set on the distal side of the cuff, the blood pressure determining means can continue to successively determine blood pressure values according to the relationship based on the pressure pulse wave detected is by the pressure pulse wave sensor.
The second object may be achieved according to a fourth aspect of the present invention, which provides a blood pressure monitor comprising an inflatable cuff which is adapted to be wound around a body portion of a living subject to press the body portion through which an artery of the subject extends; a blood pressure measuring device which measures a blood pressure of the subject by changing a pressure in the cuff; a pressure pulse wave sensor which is adapted to be pressed against a distal section of the artery located on a distal side of the cuff wound around the body portion, so as to detect a pressure pulse wave which is produced from the distal section of the artery and is propagated thereto via a skin tissue above the distal section; relationship determining means for determining a relationship between blood pressure and magnitude of pressure pulse wave, based on the blood pressure measured by the blood pressure measuring device and a magnitude of the pressure pulse wave detected by the pressure pulse wave sensor; blood pressure determining means for determining at least a mean blood pressure of the subject according to the determined relationship based on a mean magnitude of each of successive first heartbeat-synchronous pulses of the pressure pulse wave detected by the pressure pulse wave sensor; cuff-pressure increasing means for increasing the pressure of the cuff at a predetermined rate; pulse-area calculating means for calculating an area defined by each of successive second heartbeat-synchronous pulses of the pressure pulse wave which are detected by the pressure pulse wave sensor when the pressure of the cuff is increased at the predetermined rate by the cuff-pressure increasing means; half-area identifying means for identifying that the pulse areas calculated by the pulse-area calculating means have decreased to half an initial pulse area obtained before the cuff-pressure increasing means starts increasing the pressure of the cuff; and judging means for judging whether the determined relationship is accurate, based on at least one mean blood pressure determined by the blood pressure determining means and a pressure of the cuff corresponding to a time when the half-area identifying means identifies that the pulse areas calculated by the pulse-area calculating means have decreased to half the initial pulse area.
In the blood pressure monitor in accordance with the fourth aspect of the invention, if the judging means makes a positive judgment, the relationship need not be updated. Accordingly, the blood pressure measuring device does not inflate the cuff, and the subject is prevented from being pressed by the cuff. In addition, although the pressure pulse wave sensor is set on the distal side of the cuff, the blood pressure determining means can continue to successively determine blood pressure values according to the relationship based on the pressure pulse wave detected by the pressure pulse wave sensor.
The second object may be achieved according to a fifth aspect of the present invention, which provides a blood pressure monitor comprising an inflatable cuff which is adapted to be wound around a body portion of a living subject to press the body portion through which an artery of the subject extends; a blood pressure measuring device which measures a blood pressure of the subject by changing a pressure in the cuff; a pressure pulse wave sensor which is adapted to be pressed against a distal section of the artery located on a distal side of the cuff wound around the body portion, so as to detect a pressure pulse wave which is produced from the distal section of the artery and is propagated thereto via a skin tissue above the distal section; relationship determining means for determining a relationship between blood pressure and magnitude of pressure pulse wave, based on the blood pressure measured by the blood pressure measuring device and a magnitude of the pressure pulse wave detected by the pressure pulse wave sensor; blood pressure determining means for determining a blood pressure of the subject according to the determined relationship based on a magnitude of each of successive first heartbeat-synchronous pulses of the pressure pulse wave detected by the pressure pulse wave sensor; cuff-pressure regulating means for increasing the pressure of the cuff up to a predetermined value and holding the cuff pressure at the predetermined value; pulse-area calculating means for calculating an area defined by each of successive second heartbeat-synchronous pulses of the pressure pulse wave which are detected by the pressure pulse wave sensor when the cuff pressure is held at the predetermined value by the cuff-pressure regulating means; and judging means for judging whether the determined relationship is accurate, based on a ratio of the calculated area of at least one the second heartbeat-synchronous pulse of the pressure pulse wave detected by the pressure pulse wave when the cuff pressure is held at the predetermined value by the cuff-pressure regulating means, to an initial pulse area obtained before the cuff-pressure regulating means starts increasing the cuff pressure.
In the blood pressure monitor in accordance with the fifth aspect of the invention, if the judging means makes a positive judgment, the relationship need not be updated. Accordingly, the blood pressure measuring device does not inflate the cuff, and the subject is prevented from being pressed by the cuff. In addition, although the pressure pulse wave sensor is set on the distal side of the cuff, the blood pressure determining means can continue to successively determine blood pressure values according to the relationship based on the pressure pulse wave detected by the pressure pulse wave sensor.
The first object may be achieved according to a sixth aspect of the present invention, which provides a blood pressure monitor comprising an inflatable cuff which is adapted to be wound around a body portion of a living subject to press the body portion through which an artery of the subject extends; a blood pressure measuring device which measures a blood pressure of the subject by changing a pressure in the cuff; a cuff pulse wave sensor which detects a cuff pulse wave which is a pressure oscillation produced in the cuff; a distal pulse wave sensor which detects a distal pulse wave from a distal section of the artery located on a distal side of the cuff wound around the body portion; cuff-pressure increasing means for increasing the pressure of the cuff at a predetermined rate; first peak-interval determining means for determining a first interval between an upper-peak point and a lower-peak point of each of first heartbeat-synchronous pulses of the distal pulse wave which are detected by the distal pulse wave sensor when the pressure of the cuff is increased at the predetermined rate by the cuff-pressure increasing means; second peak-interval determining means for determining a second interval between an upper-peak point and a lower-peak point of each of second heartbeat-synchronous pulses of the cuff pulse wave which are detected by the cuff pulse wave sensor when the pressure of the cuff is increased at the predetermined rate by the cuff-pressure increasing means; difference determining means for determining a difference between the first interval of the each of the first heartbeat-synchronous pulses and the second interval of a corresponding one of the second heartbeat-synchronous pulses; and blood pressure determining means for determining, as a diastolic blood pressure of the subject, a pressure of the cuff corresponding to a time when the differences determined by the difference determining means significantly largely change.
In the blood pressure monitor in accordance with the sixth aspect of the invention, the upper-peak and lower-peak points of each pulse of the cuff pressure wave are not influenced by the increasing of the cuff pressure, whereas the upper-peak and lower-peak points of each pulse of the distal pulse wave are influenced by the increasing of the cuff pressure, because the distal pulse wave sensor is set on the distal side of the cuff. Therefore, the peak-interval differences are influenced by the increasing of the cuff pressure. The Inventors have found that the phase of the distal pulse wave has a certain relationship with that of the cuff pulse wave and that this relationship significantly largely changes when the cuff pressure becomes equal to a diastolic pressure of the subject. Thus, a cuff pressure corresponding to the time when the peak-interval differences significantly largely change, can be determined as a diastolic pressure of the subject. In the case where a physiological change such as arrhythmia occurs to the heart of the patient, respective waveforms of the cuff pulse wave and the distal pulse wave change in a similar manner, therefore the peak-interval differences are not influenced by this change. Thus, the diastolic BP value of the subject can be determined with high accuracy. The distal pulse wave sensor may be provided by a sensor employed for a different purpose from monitoring the blood pressure of the subject. In this case, the total number of sensors which are worn on the subject is reduced as compared with the case where an exclusive distal pulse wave sensor is employed. Although the distal pulse wave sensor is worn at a position downstream of the cuff, a measurement using the distal pulse wave sensor, different from the blood pressure measurement, can be continued without being interrupted due to the inflation of the cuff, because in a BP monitoring operation the cuff pressure is not increased to values higher than the diastolic pressure of the subject.
According to a preferred feature of the sixth aspect of the invention, the distal pulse sensor comprises a pressure pulse wave sensor which is adapted to be pressed against the distal section of the artery via a skin tissue above the distal section, so as to detect a pressure pulse wave which is produced from the distal section and is propagated thereto via the skin tissue.
According to another feature of the sixth aspect of the invention, the distal pulse senior comprises a photoelectric pulse wave sensor which emits a plurality of lights having different wavelengths toward the distal section of the artery via a skin tissue above the distal section, and detects a photoelectric pulse wave representing respective intensities of the lights reflected from the distal section via the skin tissue or transmitted through the body portion. The photoelectric pulse wave sensor may be employed for measuring a peripheral blood circulation or a blood oxygen saturation of a living subject. The manner of measurement of peripheral blood circulation is disclosed in, e.g., Japanese Patent Application laid open for inspection purposes under Publication No. 5(1993)-115445, and the manner of measurement of blood oxygen saturation is disclosed in, e.g., Japanese Patent Application laid open for inspection purposes under Publication No. 50(1975)-128387.
The second object may be achieved according to a seventh aspect of the present invention, which provides a blood pressure monitor comprising an inflatable cuff which is adapted to be wound around a body portion of a living subject to press the body portion through which an artery of the subject extends; a blood pressure measuring device which measures a blood pressure of the subject by changing a pressure in the cuff; a pressure pulse wave sensor which is adapted to be pressed against a distal section of the artery located on a distal side of the cuff wound around the body portion, so as to detect a pressure pulse wave which is produced from the distal section of the artery and is propagated thereto via a skin tissue above the distal section; relationship determining means for determining a relationship between blood pressure and magnitude of pressure pulse wave, based on the blood pressure measured by the blood pressure measuring device and a magnitude of the pressure pulse wave detected by the pressure pulse wave sensor; blood pressure determining means for determining at least a diastolic blood pressure of the subject according to the determined relationship based on a magnitude of a lower-peak point of each of successive first heartbeat-synchronous pulses of the pressure pulse wave detected by the pressure pulse wave sensor; cuff-pressure increasing means for increasing the pressure of the cuff at a predetermined rate; a cuff pulse wave sensor which detects a cuff pulse wave which is a pressure oscillation produced in the cuff; first peak-interval determining means for determining a first interval between an upper-peak point and a lower-peak point of each of first heartbeat-synchronous pulses of the distal pulse wave which are detected by the distal pulse wave sensor when the pressure of the cuff is increased at the predetermined rate by the cuff-pressure increasing means; second peak-interval determining means for determining a second interval between an upper-peak point and a lower-peak point of each of second heartbeat-synchronous pulses of the cuff pulse wave which are detected by the cuff pulse wave sensor when the pressure of the cuff is increased at the predetermined rate by the cuff-pressure increasing means; difference determining means for determining a difference between the first interval of the each of the first heartbeat-synchronous pulses and the second interval of a corresponding one of the second heartbeat-synchronous pulses; and judging means for judging whether the determined relationship is accurate, based on at least one diastolic blood pressure determined by the blood pressure determining means and a pressure of the cuff corresponding to a time when the differences determined by the difference determining means significantly largely change.
In the blood pressure monitor in accordance with the seventh aspect of the invention, if the judging means makes a positive judgment, the relationship need not be updated. Accordingly, the blood pressure measuring device does not inflate the cuff, and the subject is prevented from being pressed by the cuff. In addition, although the pressure pulse wave sensor is set on the distal side of the cuff, the blood pressure determining means can continue to successively determine blood pressure values according to the relationship based on the pressure pulse wave detected by the pressure pulse wave sensor. Moreover, the accuracy of the relationship is judged by increasing the cuff pressure up to a value around the diastolic BP value of the patient, which does not cause the patient to feel discomfort.
According to a preferred feature of the seventh aspect of the invention, the blood pressure monitor further comprises a control device which controls, when the judging means makes a negative judgment, the blood pressure measuring means to, measure another blood pressure of the subject, controls the pulse wave sensor to detect another magnitude of the pressure pulse wave sensor, and controls the relationship determining means to determine another relationship between blood pressure and magnitude of pressure pulse wave, based on the another blood pressure measured by the blood pressure measuring device and the another magnitude of the pressure pulse wave detected by the pressure pulse wave sensor.